Vaccination is an efficient means of preventing death or disability from infectious diseases. The success of this method in the field of infectious disease has also stimulated interest in utilizing vaccination in the treatment or prevention of neoplastic disease. Despite the successes achieved with the use of vaccines, however, there are still many challenges in the field of vaccine development. Parenteral routes of administration, the numbers of different vaccinations required and the need for, and frequency of, booster immunizations all impede efforts to control or eliminate disease.
One such difficulty is lack of immunogenicity in an antigen, i.e., the antigen is unable to promote an effective immune response against the pathogen. In addition, certain antigens may elicit only a certain type of immune response, for example, a cell-mediated or a humoral response. Adjuvants are substances that enhance, augment or potentiate an immune response, and can in some instances be used to promote one type of immune response over another. Although numerous vaccine adjuvants are known, alum is the only adjuvant widely used in humans.
Dendritic cells are a heterogeneous cell population with distinctive morphology and a widespread tissue distribution (Steinman, R. M., Annu. Rev. Immunol., 9: 271-296, 1991). Dendritic cells are referred to as "professional" antigen presenting cells, and have a high capacity for sensitizing MHC-restricted T cells. Thus, there is growing interest in using dendritic cells ex vivo as tumor or infectious disease vaccine adjuvants (see, for example, Romani, et al., J. Exp. Med., 180: 83, 1994). Therefore, an agent that enhanced the ability of dendritic cells to stimulate an immune response would be of wide importance.